Graphene composites with dispersed metal or metal oxide

Abstract

Metal-graphene nanocomposites, metal-oxide-graphene nanocomposites, and method for their preparation are described. According to some embodiments, a metal salt is combined with graphite oxide (GO) to form a metal salt-GO composite. The metal salt-GO composite is reduced to a metal-graphene or metal oxide-graphene nanocomposite material. The metals may be magnetic or non-magnetic. In some embodiments, the reduction is conducted via exposure to intensified electromagnetic radiation, such as focused solar radiation.

What is claimed is: 
     
         1 . A method of making a metal/metal oxide nanoparticle dispersed graphene nanocomposite, the method comprising:
 providing a substantially solid metal salt-graphite oxide composite; and   exposing the metal salt-graphite oxide composite to intensified electromagnetic radiation to form the metal/metal oxide nanoparticles dispersed graphene nanocomposite by reducing the metal salt to a metal or metal oxide and the graphite oxide to graphene.   
     
     
         2 . The method of  claim 1 , wherein the electromagnetic radiation is selected from visible light, sunlight, simulated sunlight, a combination thereof, a selected portion thereof, or a combination of selected portions thereof intensified to suitable power. 
     
     
         3 . The method of  claim 1 , wherein the intensified electromagnetic radiation provides about 0.65 W/cm 2 -1.95 W/cm 2 . 
     
     
         4 . The method of  claim 1 , wherein the intensified electromagnetic radiation causes a temperature increase to about 300° C. to about 400° C. 
     
     
         5 . The method of  claim 1 , wherein, prior to the exposing step, the intensified electromagnetic radiation is provided by at least one of:
 a) passing electromagnetic radiation through at least one refractile material;   b) passing the electromagnetic radiation through at least one converging lens; and   c) reflecting the electromagnetic radiation off of one or more converging mirrors.   
     
     
         6 . The method of  claim 1  wherein the exposing step is performed for no more than about 10 minutes per 100 mg of metal salt-graphite oxide composite. 
     
     
         7 . The method of  claim 1 , wherein the metal salt-graphite oxide composite comprises a metal salt selected from iron salts, copper salts, nickel salts, gold salts, silver salts, platinum salts, palladium salts, cobalt salts, zinc salts, cerium salts and ruthenium salts, and combinations thereof. 
     
     
         8 . The method of  claim 1  wherein the metal salt-graphite oxide composite comprises a metal salt selected from halide salts, sulphate salts, acetate salts, and nitrate salts of iron, copper, nickel, gold, silver, platinum, palladium, cobalt, ruthenium and combinations thereof. 
     
     
         9 . The method of  claim 1 , wherein the metal salt-graphite oxide composite comprises a metal salt selected from FeCl 2 , CuCl 2 , CoCl 2 , NiCl 2 , AgCl, HAuCl 2 , HAuCl 4 , AgNO 3 , H 2 PtCl 6 , H 2 PdCl 4 , RuCl 2 , Co(NO 3 ) 2 , AgC 2 H 3 O 2 , CuSO 4 , FeSO 4 , SnCl 2 , ZnCl 2 , (NH 4 ) 2 Ce(NO 3 ) 6 , CrCl 3 , metal acetates and combinations thereof. 
     
     
         10 . The method of  claim 1 , wherein the intensified electromagnetic radiation reduces the metal salt to a metal or metal oxide and the graphite oxide to graphene. 
     
     
         11 . The method of  claim 1 , wherein the metal salt-graphite oxide composite comprises a metal salt selected from AgCl, HAuCl 4 , HAuCl 2 , HAuCl 4 , AgNO 3 , H 2 PtCl 6 , H 2 PdCl 4 , RuCl 2 , SnCl 2 , ZnCl 2 , (NH 4 ) 2 Ce(NO 3 ) 6 , CrCl 3 , and metal acetates, which is reduced to a corresponding metal selected from Ag, Au, Pt, Pd, Ru, Sn, Ce and Cr. 
     
     
         12 . The method of  claim 1 , wherein the metal salt-graphite oxide composite comprises a metal salt selected from FeCl 2 , CuCl 2 , CoCl 2  NiCl 2 , SnCl 2 , ZnCl 2 , (NH 4 ) 2 Ce(NO 3 ) 6 , and CrCl 3 , which is reduced to a corresponding metal oxide selected from Fe 2 O 3 , CuO, CoO, NiO, SnO 2 , ZnO, CeO 2 , and CrO 2 . 
     
     
         13 . The method of  claim 1 , wherein the substantially solid metal salt graphite oxide composite is prepared by:
 dispersing graphite oxide in a solvent to form a dispersion;   adding a metal salt to the dispersion; and   drying the resultant material to yield a substantially solid metal salt-graphite oxide composite.   
     
     
         14 . The method of  claim 13 , wherein dispersing the graphite oxide in a solvent further comprises dispersing the graphite oxide in the solvent by ultrasonication. 
     
     
         15 . The method of  claim 13 , wherein the solvent comprises water. 
     
     
         16 . The method of  claim 1 , wherein the metal salt and graphite oxide are reduced simultaneously. 
     
     
         17 . A nanocomposite comprising:
 a graphene sheet; and   a plurality of nanoparticles of at least one metal or metal oxide dispersed on the graphene sheet.   
     
     
         18 . The nanocomposite of  claim 17 , wherein the at least one metal or metal oxide is selected from Fe 2 O 3 , CuO, NiO, Au, Ag, Pt, Pd, Co, Ru, CoO, RuO 2 , SnO 2 , ZnO, CeO 2 , CrO 2 , and combinations thereof. 
     
     
         19 . The nanocomposite of  claim 17 , wherein the graphene sheet defines two sides, and the nanoparticles of the at least one metal or metal oxide are dispersed substantially evenly on both the two sides of the graphene sheet. 
     
     
         20 . The nanocomposite of  claim 17 , wherein the composition comprises a plurality of graphene sheets, each of which contains dispersed nanoparticles of at least one metal or metal oxide. 
     
     
         21 . The nanocomposite of  claim 17  wherein the plurality of nanoparticles are non-magnetic nanoparticles, magnetic nanoparticles or combinations of thereof. 
     
     
         22 . The nanocomposite of  claim 17 , where the graphene sheet is coated with 10-15 nm Ag nanoparticles distributed in a face centered cubic structure of Ag. 
     
     
         23 . The composition of  claim 17 , graphene sheets are coated with about 12-18 nm Au nanoparticles with face centered cubic structure. 
     
     
         24 . The nanocomposite of  claim 17 , where the graphene sheet is coated with about 12-20 nm CuO nanoparticles, about 9-18 nm NiO nanoparticles, about 34-50 nm magnetic Fe 2 O 3  nanoparticles, or combinations thereof. 
     
     
         25 . The graphene nanocomposite of  claim 17 , wherein the nanocomposite comprises less than 2 at. % chlorine. 
     
     
         26 . The nanocomposite of  claim 17 , wherein the nanoparticles are metals, and the oxygen content in the nanocomposite is less than about 7 at. %. 
     
     
         27 . The nanocomposite of  claim 17 , wherein the nanoparticles are metal oxides, and the oxygen content in the nanocomposite is less than about 15 at. %. 
     
     
         28 . The method of  claim 4 , wherein the temperature increase is at a rate of about 75° C. per second to about 200° C. per second.